Railway light signal



Dec. 26, 1933. c. w. DALZELL 1,940,903

RAILWAY LIGHT SIGNAL Filed Dec. 10, 1931 m VENTOR.

Cla ezzce WDalzell By QRW Hi5 ATTORNEY.

Patented Dec. 26, 1933 1,940,903 RAILWAY LIGHT SIGNAL x Clarence W."Dalzell,-Swissvale, Pa, assignor to The Union Switch & Signal Company, Swissvale, "Pa., a corporation of Pennsylvania 7 Application December 10, 1931. SeriaI'NO. 580,029

7 Claims. (Cl. 246-41) l-My'invention relates to apparatus for the control of railway light signals, and'ha's for an'object the provision of novel and improved means for automatically causing alight signal to give a more restrictive indication when trafiic conditions warrant a less restrictive indication and the lamp or lamps which should give such less restrictive indication fail.

I will describe two forms of apparatus embodying my invention, and will then point novel features thereof in claims.

' In the accompanying drawing, Fig. 1 is a diagrammatic view showing one form of apparatus embodying my invention. Fig.2 is a view similar to Fig. 1, but showing a modified form of apparatus also embodying my invention.

out the Similar'reference charactersrefer to similar.

parts in each of the views. 1

Referring first to Fig. 1', the reference charac- 1 ters 3 and 4 designate the track rails'of a stretch of railway'track along which traflic normally, moves in the direction indicated by the arrow.

These rails are divided in the usual'manner by insulated joints to form a plurality of track sec- I tions, of which only one complete. section A, and

v the rear, portion of the next section B, are shown in the drawing. Section A is provided with the usual track circuit comprising'a battery 20 connected across the rails at the forward end of the 'section,:and a track relay AT connected across the rails at the rear end of the section. Sectionv B is provided with a similar track circuit involvinga track relay BT.

'Section A is alsoprovided'with a distant relay D, the circuit for which is from terminal Xof a suitable source 'of current, through front contact 18-19 of track'relay BT, winding of relay D, and front contact 1'.2 of track relay AT, to terminal Kof the same-source of current. It follows that the'distant relay D will be 'deenergized whenever either section'A or B isoccupied by a train.

Located-adjacent the entrance end of the sec-. tionA is a light signal SA, comprising threelamps G, Y andR, which lamps, when lighted, indicate proceed, caution and stop, respectively. In accordance with usualpractice, the beam projected from lamp Gmay be green,v the beam projected from lamp Y may be yellow, and the beam projected from lamp R may bered; The-indication given by lamp G is, of course, less restrictive than that given by either lamp Y or R, whereasthe indication given by lamp R is more restrictive than that given by lamp G. I

Lamp Gis-provided with a circuit which includes front contact 5-6 of 'relay AT and front contact 8-9-of relay D. Lamp Y is provided with.

a main circuit which includes front contact 5-6 of relay AT and back contact 8-'10 of relay D. Lamp R is provided with a circuit which includes back contact 5"I of relay when both sections A and B are unoccupied, lamp- G will he lighted; when section A is unoccupiedv and section B is occupied, lampY will lee-lighted;

and when section A is occupied, lamp R will be' lighted. The structure and operation of the apparatus thus far described, are in accordance withusual. and standard practice, and will be understood without further detailed explanation. The reference character C designates a light responsive device which-is exposed to rays from the proceed lamp G of signalSA. This device isso constructed that its electrical resistance .decreases with-increase in theintensityof the light to which it is exposed. This device C may, for example, be a photo-electric cell. It is providedwith a circuit-which includes arelay E, anda source of current the terminals of which; are designated X and K. The parts; areso proportioned that when the lamp G is lighted, the re-,

AT. It follows that sistance of the cell C will be, decreased to such value that relay E will be efiectively energizedy whereas, when lamp G is, not lighted, the resist-; ance of device-C will beincreased to suchvalue 'thatrelay E will become deenergized, and so will release its front contact 21-22.

, A slow-acting relay Fis provided with two cir cuits, one of which includes front contact'21--22 ofrelay E,'and the, other of which includes back contact 16-17 of relay D. .It'followsthat relay F will be energized when relay and also when relayD is de'e'nergized.

- The caution lamp Y of signal S A is provided with anauxiliary circuit whichpasses from terminal X, through front contact 56 of relay AT, front contact 8-9 of relay D,

D, and lamp Y to-terminal'K. It follows that lamp Y will be supplied with current when relays E is energized,

back contact 14'-15 of relay F, front contact 11-12 of relay AT'and'D are both energized and relay F is we released. 7 g v ;.As illustrated in Fig. 1, lamp G is lighted-be cause both thehome relay AT and the distant relay D areenergized. Device C is therefore receiving light 'rays from the lamp G,'so that relay E is energized, and relay Fis also energized. The

auxiliary circuit for caution lamp Y is therefore open, at back" contact 14-15 ofrelay F. I. will now assume that with. the parts in the 'condi% tions illustrated in Fig. 1, the proceed lamp G burnsout. The resistance of the device C will n then increase so that relay E will become deenergized, and this will result in deenergizing relay F. The auxiliary circuit for lamp Y will then become closed at back contact 14-45 of relay F, so that the caution lamp will become lighted. Instead of giving the proceed indication, then, signal SA will give the more restrictive caution indication.

Relay F is slow-releasing in character, and is provided with the auxiliary circuit through back contact 16--17, in order to avoid a momentary flash of the caution lamp Y when thesignal is changing from the caution to the proceed indication. To explain this more;in detail, I will assume that a train enters section A, and then. section B..

proceeds through this section into While the train occupies sectionB, relay AT will be energized, but relay D will be deenergized, so that the caution lamp Y will be lighted byvirtue of its main circuit. Relay F will then be energized by virtue of its auxiliary circuit through its back contact l617 of relay D. When the tra-inleaves section 13, track relay BT will be- .come energized, thereby energizing distant relay D. This will cause'lamp G to become lighted, but an interval of time will elapse before relay 3' becomes energized, and if relay F were allowed to releaseduringthisinterval, the auxiliary circuit for lamp Y would be closed, and this lamp Wouldtherefbrebecomelighted for a short interval-"of time. The-release period of relay F is at least equaltothe time-required for contact member 8 to travel from back contact 10 to front contact 9, plus'the time required for lamp G to then become lighted, plus the time re' 'quired for relay E to respond to the light rays supplied to deviceC. It follows, therefore, that during'the transition from a caution to a proceed indication there will be no momentary flash of the. caution lamp- -Y'.

' Thereason for including front contact 11-l2 of relayD inthe auxiliary circuit for lamp Y is to avoid the'possibility of a false proceed indica tionwhen the caution indication should be given. Assuming that section A is unoccupied and sec tion B is occupied, so that lamp Y should be lighted; alsoassuming that lamp Y burns out; and also assuming that relay D fails to be energized; then in the absence of front contact 1112, current would be supplied to the proceed lamp G-through front contact 5-6 ofrelay AT,

' back contact 8l0 of relay D; and back-contact 1415 of relay F. By providing front contact l1-12 in the auxiliary circuit for lamp Y, this possible false proceed indication when a'caution indication should be given, is prevented.

Referring now to'Fig. 2, the track circuits are the sameas in Fig. 1, and the control of signal SA b'yrelays AT and D is, likewise, the same as in Fig. 1. 111 Fig. 2, however, the light sensitive device C controls the distant relay D, thereby eliminating the necessity for the intermediate relay E" of Fig. l. In Fig. 2 the slow-releasing relay F is provided with a circuit which passes from terminal both energized, so that the proceed lamp G of then remain deenergized, because its pick-up circuit'is opendue to the fact that relay AT is energized. I

I will now assume that with the parts in the conditions in which they are shown in the drawing, a train moving toward the right enters section A. This will deenergize track relay AT, thereby causing signal SA to change from the proceed to the stop indication. Relay D will, of course, become deenergized because its circuit will be opened at contact 1-2 offrelay AT. Relay F' will then be energizedby virtue of its circuit which includes back contact 25'26of relay 'D and backcontact 2930 of relay AT. When a train passes from secion A into section B, relay AT will be come energized, but relay D will remain deenergized, because of the fact that itscircuit will'be open at contact 18l9 of relay BT. Lamp R will then become extinguished and lamp Y will become lighted. Relay F will remain energized by virtue of the circuit which-in'cludes-back contact 2-526 of relay D, and front contact-27-28 of relay F; When the train passes out of section B, relay D will become energized; so that signal lamp Y will become extinguished and ,lamp (3'' willbecome lighted. Relay F will reniain en'er gized by virtue of its stick circuit,"w"hi'ch includes the light responsive device C-and its own contact 27-23. Relay: F is made sufficiently slow-releasing to prevent it from opening during.

the transition from the cautionto the proceed indication ofsignalSA.

With only the apparatus illustrated in Fig. 2,

if a new lamp G is inserted in the signal. SA while relay AT is energizedthis lamp will not become lighted until-a train passes through section A, be-. cause there is noway ofcausingrelay F to become energized. The new lamp G will become lighted, however, after a train passes through. 3

sections A and B. If the immediate lighting of.

the new lamp G is desired, it can be accomplished by inserting a push button in the circuit of relay F to bridge front contact 27 28 for a sufiicient period of time to enable relay D to become energized.

It will be seen-from the foregoing, that apparatus embodying my invention provides for automatically giving a caution indication when the proceed indication should be given and the proceed lamp G is burned out. This apparatus also prevents a false indication due to a shortcircuit or any other fault which'will decrease the intensity of the light given by the proceed lamp :.G' below a predetermined value determined. byzthe characteristics of the light sensitive device C. Furthermore, apparatus similarto that shown in the drawing may be associated with the caution a front contact of said home relay and a front contact of said distant relay, a circuit for said caution lamp including a front contact of said home relay and a back contact of said distant relay, a light sensitive device exposed to the rays from said proceed lamp, a circuit including said device and an auxiliary relay whichis energized when and only when said proceed lamp is lighted, a slow releasing relay, two circuits for said'slowreleasing relay one including a front contact of said auxiliary relay and the other including a back contact of said distant relay, and an auxiliary circuit for said caution lamp including a front contact of said home relay and a front contact of said distant relay as well as a back contact of said slow-releasing relay. r

2. In combination, a home and a distant relay, a light signal having a proceed and acaution lamp, a circuit for said proceed lamp includ: ing a front contact of said home relay and a front contact of said distant relay, a circuit for said caution lamp including a front contact of said home relay and a back contact of said distant relay, a light sensitive device exposed to the rays from said proceed lamp, a circuit including said device and a slow releasing relay as well as a front contact of the latter relay, a shunt for said slowreleasing relay circuit around said device and including a back contact of said distant relay, a second shunt for said slow-releasing relay circuit around the said front contact thereof and includinga back contact of said home relay, and

a ,circuit for said distant relay controlled by a when lighted gives a more restrictive indication, a relay, means including a light responsive device exposed to the rays from said first lamp for energizing said relay when and only when the first lamp is lighted, other means for energizing said'relay when said signal should give a more restrictive indication, and means including a back contact of said relay for causing said second lamp to become lighted when said first lamp should be lighted if-the first lamp is burned out.

4. In combination, a home relay and a distant relay, a light signal having a proceed lamp and a caution lamp, means for lighting said proceed lamp when both of said relays are energized,

means for lighting said caution lamp when said home relay is energized and said distant relay is deenergized, and means including a light re sponsive device exposed to the rays from said proceed lamp for preventing said distant relay being energized unless the proceed lamp is lighted.

5. In combination, 'a railway light signal,'a main circuit for one lamp of said signal, a light responsive device exposed to the rays from another lamp in said signal, and an auxiliary circuit for said first lamp controlled by said device;

6. A multiple aspect light signal for railroads having lamps controlled according to trafilc conditions ahead, and automatic means independent of traflic conditions and involving a light sensitive device responsive to the light emitted by a less restrictive lamp for lighting a more restrictive lamp if the less restrictive lamp fails and traflic conditions are such that the less restricpendent of trafiic conditions and involving a light sensitive device responsive to rays emitted by the green lamp for lighting the yellow lamp if the green lamp fails and traffic conditions are such that the green lamp should be lighted.

. CLARENCE W. DALZELL. 

